1. Field of the Invention
The present invention relates to a display screen having color filters and a method of manufacturing the display screen. The present invention also relates to a cathode ray tube using this display screen.
2. Description of the Related Art
Red, blue, and green phosphor layers as dots or stripes are formed on the inner surface of a faceplate of a display device such as a cathode ray tube or a color television receiver. When electron beams are bombarded against the phosphor layers, the phosphor layers emit light to display an image.
In such a display device, phosphor layers have been conventionally studied to improve the image display characteristics such as a contrast and a color purity. For example, phosphor layers with filters are available in which pigment layers having the same colors as the emission colors of the phosphor layers are formed between a faceplate and the phosphor layers.
When the phosphor layers with filters are used in a display device, the red, blue, and green pigments selectively absorb the blue light component, the green light component, and blue and red light components, respectively. Therefore, the contrast and color purity of the display device are improved.
A method of manufacturing the phosphor layers with filters is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-275008. According to this prior art, a substrate is coated with a resist, and a region except for predetermined positions on the substrate is exposed with light to form a resist pattern on the substrate. The resist pattern is coated with a pigment solution, and the resist pattern and the pigment layer on the resist pattern are removed by acid decomposition to form a pigment pattern at the predetermined positions, thereby obtaining a pigment layer of each color.
Another method of forming a pigment layer is disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 5-275007. A substrate is coated with a pigment dispersion obtained by mixing an aqueous polymer such as polyvinyl alcohol (PVA) or polyvinyl pyrrolidone (PVP) with a crosslinking agent such as ammonium dichromate (ADC) or diazonium salt, and exposure and development with warm water are performed, thereby forming a pigment layer having a predetermined pattern.
In the above patterning, however, a patterning process consisting of exposure and development must be repeated three times to obtain, e.g., pigment layers of three colors. The number of steps in the manufacture undesirably increases. Strong demand has arisen for developing a method of more easily forming a filter pattern.
The red pigment layer is good in absorbency of ultra violet among three primary colors of pigments.
In, e.g., Jpn. Pat. Appln. KOKAI Publication No. 5-275007, it is difficult to form a red pigment layer consisting of one of pigments of three primaries by patterning process comprising exposure and development since ultra violet is absorbed by the red pigment layer so that a resist cannot be harden sufficiently.